1. Field of the Invention
The invention relates to novel m-dihydroxybenzene derivatives and to agents for dyeing keratin fibers containing these compounds.
2. Description of the Related Art
In the area of keratin fiber dyeing, particularly hair dyeing, oxidation dyes have attained substantial importance. In this case, the coloration is produced by reaction of certain developers with certain couplers in the presence of an appropriate oxidant. Suitable developers are, in particular, 2,5-diaminotoluene, 2,5-diaminophenylethyl alcohol, p-aminophenol, 1,4-diaminobenzene and 4,5-diamino-1-(2-hydroxyethyl)pyrazole, and suitable couplers are, for example, resorcinol, 2-methylresorcinol, 1-naphthol, 3-aminophenol, m-phenylenediamine, 2-amino-4-(2′-hydroxyethyl)aminoanisole, 1,3-diamino-4-(2′-hydroxyethoxy)-benzene and 2,4-diamino-5-fluorotoluene.
The oxidation dyes used for dyeing human hair must meet numerous requirements in addition to that of being able to produce colorations of the desired intensity. For example, these dyes must be harmless from a toxicological and dermatological standpoint, and the hair colorations obtained must have good light fastness, resistance to permanent waving, acid fastness and rubbing fastness. In any case, however, in the absence of exposure to light, rubbing and chemicals, such colorations must remain stable over a period of at least 4 to 6 weeks. Moreover, by combining appropriate developers and couplers, it must be possible to create a wide range of different color shades.
Attempts have already been made to improve the properties of m-dihydroxybenzenes by introduction of substituents. Thus, for example, resorcinols substituted in the 4-position are known from European Unexamined Patent Application EP 0 904 774 and WO Unexamined Patent Application 99/15148. Moreover, German Unexamined Patent Applications DE 30 016 905 and DE 198 59 800 teach the use of substituted m-dihydroxybenzenes in oxidation hair colorants. With the currently known dyeing agents, however, it is not possible to meet the requirements placed on dyeing agents in all respects. Hence, the need continued to exist for novel couplers that would meet the aforesaid requirements to a particularly high degree.